The studies proposed here are designed to investigate patterns of eating in lean and obese humans. Since it seems likely that obesity is a heterogenous disorder, we expect that obese people will show a wide range of eating patterns, many of which will differ instructively from the eating patterns of lean people. Two aspects of eating behavior will be studied: the microstructure of meals and 24-hour eating patterns. Microstructure will include the patterns of chewing and swallowing within a meal, revealing the initial rate of eating, changes in rate, duration, and total amount of eating before the asymptote of satiation is reached. The 24-hour eating pattern will include meal and snack times, their durations, sizes, and frequency as well as the intermeal intervals. The first experiments will explore the comparative meal patterns of lean and obese subjects in the laboratory with the use of newly-developed solid food unit (SFU). The second series of experiments will study microstructure of meals with an intra-oral sensor that records all chews and swallows of SFUs as well as of complex foods. The third series of experiments will monitor eating patterns objectively and unobtrusively by telemetering to a 24-hour tape recorder worn on the belt all oral sensor data on chews, swallows, and drinking. These experiments will make possible for the first time the comparison of the patterns of eating of lean people and a variety of obese people in their natural environments and will show how they respond to some of the major variables known to affect meals and daily eating patterns. The fruits of these investigations may include the possibility of a behavioral classification of the obesities, specific recommendations for behavioral control of eating, monitoring of compliance with diet programs, and even the possibility of continuous monitoring and signalling patients when they eat too fast, too long, or too often.